Blower



Jan. 12, 1965 w. H. WENTLING ETAL 3,155,258

BLOWER Filed April 4, 1963 INVENTORS WILLIAM H.WENTLING, BY DONALD akmswon'rm a WILLIAM R POWELL ATTORNEYS Unimd States patenft BLOWER William H. Wentling, Donald D. Kinsworthy, and William P. Powell, Dayton, Ohio, assignors to The Lau Blower Company, Dayton, hio,-a corporation of Ohio Filed'Apr. 4, 1963, Ser. No. 270,582

' .4 Claims. (Cl. 230- -13t) ---This invention relates to centrifugal blower wheels, and particularly to fabricated blower wheels which have forwardly curved blades.i'- I Two of the more prevalentrexpedients utilized for the construction of blower wheels are the single'blade sheet type wherein the blades .are cut in an integral sheet which is then formed into awheel, andthe individual blade type wherein a plurality'of separate blades is secured between a pair'of end rings. The latter type is much more acceptable from the standpoint of performance in that the bladestcan' behspaced around' the periphery of the wheel to achieve higher efficiency, whereas in the blade sheet type wheel, the spacing between the blades is usually fixed so that thistype of wheel is not satisfactory for use where highperformanoe is desired.

The use of individually fabricated blades often limits the curvature ofthe blade surface 'so that the leading edges of lthe blades arenot tangential to the blower wheel and there are large energy losses ,due to the impacting of the air on the trailing edges of'the blades. Without a tangential blade tip, the outlet velocity from the wheel is much less thus decreasing the velocity pressure produced thereby. The individual blade type blower Wheel In-the drawings- FIG. 1 is a perspective view of the blower wheel looking through the inlet end thereof;

FIG. 2 is "a perspective view of one of the individual blades utilized in the blower wheel shown in FIG. 1;

ring after-the spinning operation;

FIG. 7"is a sectional view t'aken essentially along the line '77 of FIG. 5i a I FIG. 8 is another sectional view takenessentially along '1 the line 8 -8 of FIG. 6; 7'

also suffers from the disadvantage that the end rin'gs have an outer diameter larger than the outer diameter of the blades. Thus a nine-inch blower wheel does not have a nine-inch outside diameter at the blade tips, and this loss in the diameter decreases the efiiciency of the wheel since the centrifugal force exerted by such a blower wheel is proportional to theblade diameter thereof.

Another important consideration in thedesign of this type of 'wheel isthat the blades .must be secured to the end ring and backiplate so that they are rigidly supported against any. substantial fiexure as a result of high speed rotation of the wheel. This connection. between the blades and end ring also must not restrict the flow of air through the open end of the wheel, and furthermore must permit themost'desirable blade configuration and mounting angle.

Accordingly, it is an object of this invention to provide an improved blower wheel having individual blades of optimum configurationand circumferential spacing for improved efliciency thereof, and particularly to provide a blower wheel-having an outer blade diameter substantially equal to the outer diameter of the end ring and back plate. 7

Another object of this invention is to provide a fabricated centrifugal blower wheel having individual blades secured at one end to an end ring in such a manner that the flow of air into the blower wheel is not impeded and a substantially rigid connection is provided capable of withstanding the centrifugal forces exerted thereon by high speed rotation of the blower wheel.

I A further object of this invention is to provide a blower wheel of the aforesaid type having individual blades which are easilymanufactured and have an optimum con-.

figuration for providing maximum capacity to the blower assembly, and further to provide ablower wheel of the above type which can beinexpensively fabricated from numerous types of materials.

Otherobjects and advantages of the invention-will be apparent from the following description, the accompanying drawings and the appended claims.

' FIG; 9 is a schematic diagram of the forces generated by the individual blades; and v FIG. 10 is a fragmentary view of the flange portion of the blade taken along the view line 10-10, of FIG. 3.

Referring to the drawingswherein a preferred embodiment of the invention is shown, FIG. 1 shows a centrifugal blower wheel 10 including 'a plurality of parallel blades 11 which form the circumferential sides ofthe blower wheel and are held securely in position by the end ring 12 and back plate 13,. A hub 15 is secured to the back plate 13 for mounting the'blower wheel on a drive shaft in the'usual manner, and the screw 16 (FIG. 4) in thehub 15 is utilized to lock the blower wheel 10 g I to the drive shaft. The blades 11 are preferably formed and the ,blower wheel 10 fa bricated inaccordan'ce with the process and apparatus disclosed in thecopending application of William H. Wentling and William P. Powell, for Centrifugal Fan, Serial No. 215,988, filed August 9, 1962, and assigned to the assignee of this invention.

Each blade 11 is constructed of a relatively thin sheet metal, such as steel or aluminum, and includes a blade surface '20 (FIG. 2) having leading and trailing .edges 21 and 22 with the blade surface 20 being arcuately formed about a radius r having a center at 24, as shown in FIG; 9. The blade surface 20 preferably extends through slightly more than 90. to provide maximum surface area while permitting the production of the blade 10 'by suitable die stamping or apparatus, such as shownin the aforesaid copending application, which limits the degree of deformation to that which permits the blade to be stripped from the die. Moreover, this full blade surface 20 makes it possible for the leading edge 21 to I be in a tangential plane whereas the trailing edge 22 extends inwardly generally in a radial direction.

Identical extensions 26 project longitudinally from each end of each blade 11 adjacent-the leading portion of the blade surface 20 for use in securing the blades 11 to the end ring 12 and back plate 13. Each of the extensions includes a tapered section 27 having an axially extending shoulder 28 at its outer end from the outer edge of which the upturned flange 30 projects in a plane parallel" to the leading edge 21 of the particular blade under consideration. The edge 32 of each shoulder 30 also lies radially inwardly of the wheel from the leading blade edges 21 so that the outer diameter of the end ring 12 and back plate 13 will be substantially equal to the outer diameter of the blower wheel at the blades.

As seen in FIG. 3, one-half of the flange 30 and shoulder 28 project forwardly of the leading edge 21 for mounting the leading edge 21 of the blade 11 tangentially of the wheel. This arrangement makes possible production of the blades by stamping from an elongated strip of metal as described in the aforesaid copend-ing application. That is, in order to provide leading and trailing edges 21*and 22- which are-nearly perpendicular to formation which results from, unusual stresses.

3 I each other, the leading edge must be horizontal in the die and therefore parallel to the flange 30.

The end ring 12 and back plate 13, as seen in FI GS. and 6, have identical outer peripheralconstrucnons which 'includeaygroove 35 for receiving the extensions 26 for each blade 11. The grooves 35 are defined by'an inner suppport wall 36 which supports the lower surface 37 of the shoulder 28, a radial'sidewall 40'which engages the outermost side wall 41 of the flanges 30, and the upper deformable wall 43 which is spun over theinner side 44 of the flange 30 and the top, surfaceAS of the shoulder '28, The side edge '47 of the blade surface is compressed against the radially inwardly extending lip- 48 during the spinning operation thus, giving the finished wheel additional resistance to twisting and similar de- Thus the end ring 12 and back plate 13 rigidly lock the blades 11 in positionqagainst movement in any direction, with the deformed wall 43 (FIG. 5) providing effective resistanceto the radially acting centrifugal forceswhichact.

. 4 Therefore,

where 01 is the spacing of the blades at their outlet, and d is the bladespacing at their inlet.

Thus, withincertain limits, if u and d are. as large as r possible, and d isheld to a minimum, the resulting 1 velocity willbe high:

on the blades 11 when the blower wheel 10 is. rotated g at high speed. a

gentially of the-blower wheel 10-, the leading edge 21 must be in the same radial plane as the midpoint of the flange 30. The important feature, required to achieve a tangential leading edge regardless of the relative position of the surface 20 and the extension 26, is that the leading edge 21 and the center 24 of the radius of cur vature lie inthe same radial plane. Y e The centrifugal blower wheel 10 imparts velocity-to the air as a result of two forces, that is, the centrifugal force caused by rotation of the air and rotary force caused by contact between the air and the blades.

where.

As, indicated above, the direction of the outlet 'wis perpendicular .to the outlet area'be tween two adjacent blades, -or perpendicular. to a linebetween thecenter of the radius of curvature of thebladeadjacent the. previous 1 blade under consideration. Within limits the smaller-the value of d thesmaller the angle b so that the NECIOI u and w williproducea largervalue of velocity V. The theoretical total velocity pressure delivered is V P 1096.5 3 Wh P is the theoretical total velocity'pressure,

I V is the air velocity leaving'the wheel, and

p is air density, and

K is a constantequal to a 7 lXn' 1096.5- is a conversion constant. See Fan Engineering,

by Buffalo Forge Co., Buffalo, N'.Y., 5th ed. 1949, pages 98 and 99-for derivation.

lis the surface width of the blade,

'r' is the bladeradius, and

" n is the number of blades in the blower wheel shown in FI G.]9, these forces can be broken into the exit velocity w which leaves the wheel perpendicularly to, t

the outlet area between any two blades and the tangential velocity Li which leaves the wheel tangentially. The out-. let 'area lies in a plane extending through the center of blade 11a and through the leading edge 21 of the adjacent trailing blade 11b, and has a width d and length equal to the blade length. The outlet velocity V of the air is the total of the exit and tangential velocities.

which 'must have their directions, as well as their nu,- merical values, added. In order to achieve the largest possible outlet velocity V, the angle b between the exit and tangential velocities w. and u must be as -loW as possible.

Referring to FIG. 9, it is seen that the outlet velocit V leaving the outlet areabetween the blades 11a.. and

11b, is i V=u+w I 1 where V is the outlet air velocity vector,

u is. the tangential speed vector at the leading edge of.

the blade 11b, and w is the exit velocity of this blade.

sothatthe outlet velocity V and the number of blades n have the greatest influenceon the pressure P since I andr. are proportional. I a

Consequently it isseenthatthe blade edge 21 is tangentialand thus creates a relatively low angle b between the tangentialvelocity vector u and the exit velocity vector w. The full blade surface 20 permits alow-value of d andthehigh value d which results in a higher-total velocity'V thanpreviously known. This factor is an important consideration in determining the velocity pressure developed by the blower wheel.

, Moreover, the full blade surface 20 substantiallyree duces the impact force between the. airand the blade since, as the air is movedradially. outwardly from the center of thev wheel, the smoothly curved blade'surface 20--,gradually changes its direction from radial to that of theoutlet velocity V. If the blade'll had a smallersurface area on the innermost portion thereof, there would be a substantial increasein the energy dissipated bythe impact of the radially moving air with the portion of the 7 blade adjacent the trailing edge'22. The invention has provided a tangential blade edge 21' as well as a generally radial trailing blade edge. 22 to. reduce the aforesaid, losses due to impactby providing a substantially ninety degrees of blade surface 20. By way of example, the production embodiment of the invention has ninety-two degrees of blade surface.

The invention has thus, provided an improved centrifu-v gal blower wheel which is capable of highly efficient operation wherein a maximumair velocity. isgenerated thereby with minimum impact losses due to contact between the air and the'blades. The leading. edges 21 of the, blades 11 determine the outer diameter of the blower wheel since the endring 12 and back plate 13 have outer diameters which are substantiallyequal to the outer diam eter. measured at the blades 11. In addition, the end ring rigidly supports the adjacent endof the blades without adversely effecting the air flow into the blower wheel.

The invention has been illustrated in connection with a single inlet blower wheel but it should be appreciated that the invention is readily adapted for use in a double inlet wheel where the blades 10 are longer, an end ring is used in lieu of the back plate 13, and a suitable center disk is provided for supporting the blades on a drive shaft. Moreover, a double inlet blower wheel can be produced by placing two of the single inlet wheels 10 together with their back plates held rigidly by a single hub or the like.

While the form of apparatus herein described constitutes a preferred embodiment of-the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:

1. A centrifugal blower wheel comprising, a plurality of parallel separate blades circumferentially arranged to form a wheel having a predetermined outer diameter, each said blade having a smoothly curved blade surface with a predetermined radius, said blade surface having a free inner trailing edge portion and an outer leading edge portion in a direction of rotation of the wheel, said leading portion terminating in a leading edge which is substantally tangent to the wheel periphery, an integral extension on each end of each said blade projecting axially outward of said blade from said outer edge portion only and substantially forward thereof in the direction of rotation of the wheel so that the end of said blades adjacent said trailing inner edge portions are free for axial flow of air into the wheel thereby increasing the inner intake area of said wheel, said outer edge portion of said blade and said extension having a tapered portion in the area of their juncture for positioning the outermost portion of said extension radially inward of the wheel from said leading edges, said extension including a rectangular flange on said outermost portion thereof which projects perpendicularly therefrom radially outward of the wheel, said flange having upper and lower edges which are parallel to each other and to a plane extending tangentially of said wheel through said leading edge of said blade surface, and a continuous retaining ring at each end of the wheel having a groove concentric with the wheel for receiving and enclosing said flanges to position the center of curvature of said blade surface and the midpoint of said flanges attached thereto in a common radial plane with said leading edge of said blade surface so that said leading edges lie substantially tangential of the wheel, said rings having a radial inner portion which supports the radial innermost surface of said extension and lies radially outward of said free inner trailing edge portions of said blade, and an integral radial outer portion on said rings which surrounds said flange and has an outer diameter substantially equal to said predetermined diameter for locking said blades together.

2. A centrifugal blower. wheel comprising, a plurality of parallel separate blades circumferentially arranged to form a wheel having a predetermined outer diameter, each Q said blade having a smoothly curved blade surface with a predetermined radius, said blade surface having a free inner trailing edge portion and an outer leading edge portion in a direction of rotation of the wheel, said leading portion terminating in a leading edge which is substantially tangent to the wheel periphery, an integral extension on each end of each said blade projecting axially outward of said blade from said outer edge portion only and substantially forward thereof in the direction of rotation of the wheel so that the end of said blades adjacent said trailing inner edge portions are free for axial flow of air into the wheel thereby increasing the inner intake area of said wheel, said outer edge portion of said blade and said extension having a tapered portion in the area of their juncture and slightly radially depressed relative to said leading edge portion of said blade for positioning the outermost portion of said extension radially inward of the wheel from said leading edges, said extension including a rectangular flange on said outermost portion thereof which projects perpendicularly therefrom radially outward of the wheel, said flange having upper and lower edges which are parallel to each other and to a plane extending tangentially of said wheel through said leading edge of said blade surface, and a continuous retaining ring at each end of the wheel having a groove concentric with the wheel for receiving and enclosing said flanges to position the center of curvature of said blade surface and the midpoint of said flanges attached thereto in a common radial plane with said leading edge of said blade surface so that said leading edges lie substantially tangential of the wheel, said rings having a radial inner portion which supports the radial innermost surface of said extension and lies radially outward of said free inner trailing edge portions of said blade, and an integral radial outer portion on said rings whichv surrounds said flange and has an outer diameter substantially equal to said predetermined diameter for locking said blades together.

3. A blower wheel as defined in claim 2 wherein at least one of said continuous retaining rings is part of an end plate adapted to have a hub secured thereto for mount ing the wheel for rotation.

4. A blower wheel as defined in claim 2 wherein said radial inner portion of said retaining rings include a radially inward extending lip in engagement with the adjacent end of said blade surface for adding rigidity to the wheel, and at least one of said lips defining an inlet opening to the wheel free from obstruction by any portion of said extension.

References Cited in the file of this patent UNITED STATES PATENTS 2,592,851 Beranek Apr. 15, 1952 2,894,681 Lunde et al July 14, 1959 3,004,326 Merz Oct. 17, 1961 3,091,384 Delaney May 28, 1963 FOREIGN PATENTS 479,943 Canada Jan. 1, 1952 848,131 Great Britain Sept. 14, 1960 

1. A CENTRIFUGAL BLOWER WHEEL COMPRISING, A PLURALITY OF PARALLEL SEPARATE BLADES CIRCUMFERENTIALLY ARRANGED TO FORM A WHEEL HAVING A PREDETERMINED OUTER DIAMETER, EACH SAID BLADE HAVING A SMOOTHLY CURVED BLADE SURFACE WITH A PREDETERMINED RADIUS, SAID BLADE SURFACE HAVING A FREE INNER TRAILING EDGE PORTION AND AN OUTER LEADING EDGE PORTION IN A DIRECTION OF ROTATION OF THE WHEEL, SAID LEADING PORTION TERMINATING IN A LEADING EDGE WHICH IS SUBSTANTIALLY TANGENT TO THE WHEEL PERIPHERY, AN INTEGRAL EXTENSION ON EACH END OF EACH SAID BLADE PROJECTING AXIALLY OUTWARD OF SAID BLADE FROM SAID OUTER EDGE PORTION ONLY AND SUBSTANTIALLY FORWARD THEREOF IN THE DIRECTION OF ROTATION OF THE WHEEL SO THAT THE END OF SAID BLADES ADJACENT SAID TRAILING INNER EDGE PORTIONS ARE FREE FOR AXIAL FLOW OF AIR INTO THE WHEEL THEREBY INCREASING THE INNER INTAKE AREA OF SAID WHEEL, SAID OUTER EDGE PORTION OF SAID BLADE AND SAID EXTENSION HAVING A TAPERED PORTION IN THE AREA OF THEIR JUNCTURE FOR POSITIONING THE OUTERMOST PORTION OF SAID EXTENSION RADIALLY INWARD OF THE WHEEL FROM SAID LEADING EDGES, SAID EXTENSION INCLUDING A RECTANGULAR FLANGE ON SAID OUTERMOST POSTION THEREOF WHICH PROJECTS PERPENDICULARLY THEREFROM RADIALLY OUTWARD OF THE WHELL, SAID FLANGE HAVING UPPER AND LOWER EDGES WHICH ARE PARALLEL TO EACH OTHER AND TO A PLANE EXTENDING TANGENTIALLY OF SAID WHEEL THROUGH SAID LEADING EDGE OF SAID BLADE SURFACE, AND A CONTINUOUS RETAINING RING AT EACH END OF THE WHEEL HAVING A GROOVE CONCENTRIC WITH THE WHEEL FOR RECEIVING AND ENCLOSING SAID FLANGES TO POSITION THE CENTER OF CURVATURE OF SAID BLADE SURFACE AND THE MIDPOINT OF SAID FLANGES ATTACHED THERETO IN A COMMON RADIAL PLANE WITH SAID LEADING EDGE OF SAID BLADE SURFACE SO THAT SAID LEADING EDGES LIE SUBSTANTIALLY TANGENTIAL OF THE WHEEL, SAID RINGS HAVING A RADIAL INNER PORTION WHICH SUPPORTS THE RADIAL INNERMOST SURFACE OF SAID EXTENSION AND LIES RADIALLY OUTWARD OF SAID FREE INNER TRAILING EDGE PORTIONS OF SAID BLADE, AND AN INTEGRAL RADIAL OUTER PORTION ON SAID RINGS WHICH SURROUNDS SAID FLANGE AND HAS AN OUTER DIAMETER SUBSTANTIALLY EQUAL TO SAID PREDETERMINED DIAMETER FOR LOCKING SAID BLADES TOGETHER. 